News

BPA in Cans and Plastic Bottles Linked to Quick Rise in Blood Pressure

By ANAHAD O'CONNOR

December 8, 2014

People who regularly drink from cans and plastic bottles may want to reconsider: A new study shows that a common chemical in the containers can seep into beverages and raise blood pressure within a few hours.

The research raises new concerns about the chemical bisphenol A, or BPA, which is widely found in plastic bottles, plastic packaging and the linings of food and beverage cans. Chronic exposure to BPA, as it is commonly known, has been associated with heart disease, cancer and other health problems. But the new study is among the first to show that a single exposure to the chemical can have a direct and fairly immediate impact on cardiovascular health.

The study found that when people drank soy milk from a can, the levels of BPA in their urine rose dramatically within two hours – and so did their blood pressure. But on days when they drank the same beverage from glass bottles, which don’t use BPA linings, there was no significant change in their BPA levels or blood pressure.

A single instance of increased blood pressure may not be particularly harmful. But the findings suggest that for people who drink from multiple cans or plastic bottles every day, the repeated exposure over time could contribute to hypertension, said Dr. Karin B. Michels, an expert on BPA who was not involved in the new research.

Dr. Michels said that the design of the new study was impressive and its findings “concerning.” About 30 percent of adults nationwide have hypertension, and BPA exposure is ubiquitous.

“I think this is a very interesting and important study that adds to the concern about bisphenol A,” said Dr. Michels, an associate professor at Harvard Medical School and Brigham and Women’s Hospital. “It raises a lot of questions. We have such a high rate of hypertension in this country, which has risen, and we haven’t really thought of bisphenol A and its use in cans as one of the causes of that. ”

BPA has been used since the 1960s to make countless everyday products like plastic bottles, food containers, contact lenses, and even sippy cups and baby bottles. The chemical can leach into food, and studies show that the vast majority of Americans who are tested have BPA in their urine.

Not everyone is convinced that BPA poses a risk to consumers. The American Chemistry Council, an industry trade group, has said BPA is safe and has opposed federal and state legislative proposals to ban it.

Much of the evidence against BPA comes from large population studies rather than controlled clinical trials. A number have linked high urinary levels of BPA to a greater risk of hypertension and heart and peripheral artery disease. But those studies simply show correlations, and do not provide evidence that BPA is the cause.

The latest study, published in Hypertension, a journal of the American Heart Association, was a randomized controlled trial. The authors, a team from Seoul National University’s department of preventive medicine in Korea, recruited 60 older subjects, most of whom were women, and assigned them to drink soy milk from cans or glass bottles on three separate occasions, weeks apart. A majority had no history of high blood pressure, though some did.

The researchers chose soy milk because it does not have any properties that are known to increase blood pressure. And unlike soda, fruit juice and other acidic beverages, which are more likely to leach BPA from containers, soy milk is considered fairly neutral.

When the subjects drank from glass bottles, the study found, their urinary BPA levels remained fairly low. But within two hours of drinking from a can, their levels of BPA were about 16 times higher.

As BPA levels rose, so too did systolic blood pressure readings – on average by about five millimeters of mercury. In general, every 20 millimeter increase in systolic blood pressure doubles the risk of cardiovascular disease.

BPA is known to block certain estrogen receptors that are thought to be responsible for repairing blood vessels and controlling blood pressure. The chemical may also affect blood pressure indirectly by disrupting thyroid hormone, the authors noted.

“Clinicians and patients – particularly hypertension or cardiovascular disease patients – should be aware of the potential clinical problems for blood pressure elevation when consuming canned food and beverages,” said Dr. Yun-Chul Hong, an author of the study and director of the Institute of Environmental Medicine at Seoul National University.

He recommended that people choose fresh foods and glass bottles over cans and plastic containers, and he urged manufacturers “to develop and use healthy alternatives to BPA for the inner lining of can containers.”

Because of growing consumer concerns, some bottles and packaged food products now carry “BPA free” claims on their labels. However, these products often contain chemically similar alternatives – like bisphenol S. One study in the journal Environmental Health Perspectives found that plastic products advertised as BPA-free still leached chemicals with estrogenic activity – and some of these chemicals were even more potent than BPA.

Dr. Michels, at Harvard, who published a prominent study on BPA exposure , said she tries to avoid eating or drinking foods from cans and plastic bottles, and drinks carbonated water from glass bottles. She said labels that say “BPA free” do nothing to assuage her concerns.

“It doesn’t have bisphenol A, but on the other hand I worry that the new chemical they put in there may also be a problem,” she said. “Exchanging one chemical for another doesn’t make me feel comfortable.”